Ink cartridge

ABSTRACT

An ink cartridge is detachably mounted on a cartridge holder. At least one first reflector is provided in the cartridge holder. A reflective-type optical sensor includes a light emitter and a light receiver. The optical sensor is operable to form an optical path originated from the light emitter to the light receiver via the first reflector. A shading member is provided in the ink cartridge operable to shade the optical path when the ink cartridge is mounted on the cartridge holder. A second reflector is provided in the ink cartridge. The second reflector reflects light emitted from the light emitter and varies an intensity thereof in accordance with an ink amount remaining in the ink cartridge.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.11/831,511, filed Jul. 31, 2007 now U.S. Pat. No. 7,883,191, which is acontinuation of U.S. patent application Ser. No. 11/409,068, filed Apr.24, 2006, now U.S. Pat. No. 7,261,403; which is a continuation of U.S.patent application Ser. No. 10/413,578, filed Apr. 15, 2003, now U.S.Pat. No. 7,044,590, which claims the benefit of Japanese PatentApplication No. 2002-113940, filed Apr. 16, 2002, the entire contents ofeach of which are hereby incorporated by reference in this application.

BACKGROUND OF THE INVENTION

The present invention relates to an ink cartridge detector operable todetect whether or not an ink cartridge is properly mounted on acartridge holder. The invention also relates to an ink jet printerprovided with the above mentioned ink cartridge detector, and to the inkcartridge to be employed in the above mentioned ink cartridge detector.

There has been widely used an ink jet printer of a type that printscharacters and images on a printing medium by discharging ink which issupplied from an ink tank onto the printing medium through a print head.In the ink jet printer of this type, the ink tank of a cartridge system(hereinafter referred to as an “ink cartridge”) has been widely employedso as to facilitate supply of the ink.

In the above described ink jet printer, it has been required to detectan amount of remaining ink in the ink cartridge and a mounting conditionof the ink cartridge for the purpose of preventing defective printingdue to shortage of the remaining ink in the ink cartridge or incompletemounting of the ink cartridge, or for the purpose of issuing an alarmindicating the shortage or the incomplete mounting. For this reason,there have been proposed mechanisms for enabling the amount of theremaining ink and the incomplete mounting of the ink cartridge to bedetected by a single optical sensor of the reflective type (disclosed inJapanese Patent Publications Nos. 10-230616A and 9-174877A, forexample).

In the above described detectors, a light beam is emitted from theoptical sensor onto two reflectors (prisms) which are provided in abottom of the ink cartridge, and the amount of the remaining ink and themounting condition are detected on the basis of amounts of reflectivelight beams received from the reflectors. Specifically, the reflectorfor detecting the amount of the remaining ink is transparent so thatreflectivity (intensity of reflected light) may vary according to theamount of the remaining ink, while the reflector for detecting themounting condition is mirror-finished so that the light can be reflectedirrespective of the amount of the remaining ink.

However, in the above described related-art ink jet printer, there havebeen such problems as described below.

i) It has been necessary for the ink cartridge to be provided with tworeflectors which are formed of separate members, and hence, the numberof components and production steps are increased, creating a high costfor the ink cartridge.

ii) Because the reflectors of the ink cartridge are exposed inside theprinter even when a printing operation is performed, there has been sucha possibility that spots such as ink splashed during the printingoperation might adhere to the reflectors to make the detection by theoptical sensor unstable.

iii) When the optical sensor has received the reflective light, it isdecided that the ink cartridge has been properly mounted. Therefore,when the optical sensor has received an exterior turbulent light, it hasbeen liable to be decided that the ink cartridge has been properlymounted, even though the ink cartridge has not yet been mounted. Assuch, the printing operation might be commenced without proper mountingof the ink cartridge.

SUMMARY OF THE INVENTION

It is an object of the invention to provide an ink cartridge detector,in which necessity for providing an ink cartridge with a reflector fordetecting the mounting condition can be eliminated although the mountingcondition of the ink cartridge is detected by an optical sensor ofreflective type, whereby not only reduction of cost for the inkcartridge can be attained, but also an erroneous recognition of themounting condition due to soils or ink splash on the reflector or anexterior turbulent light can be prevented.

It is also an object of the invention to provide an ink jet printerincorporating such an ink cartridge detector, and an ink cartridgedetected by such an ink cartridge detector.

In order to achieve the above objects, according to the invention, thereis provided an ink cartridge detector, comprising:

an ink cartridge;

a cartridge holder, on which the ink cartridge is detachably mounted;

at least one first reflector, provided in the cartridge holder;

a reflective-type optical sensor, including a light emitter and a lightreceiver, the optical sensor operable to form an optical path originatedfrom the light emitter to the light receiver via the first reflector;and

a shading member, provided in the ink cartridge operable to shade theoptical path when the ink cartridge is mounted on the cartridge holder.

The first reflector may be integrally fixed on a bottom portion of thecartridge holder. In such a configuration, not only the structure can besimplified, but also reliability of detecting the mounting condition ofthe ink cartridge can be enhanced, in comparison with a case where thereflector is provided as a movable member.

Further, the shading member may be integrally formed with the inkcartridge at a lower portion thereof (a downstream portion with regardto an inserting direction of the ink cartridge with respect to thecartridge holder). In such a configuration, the number of components andproduction steps of the ink cartridge can be reduced.

The ink cartridge may be formed with a recess which covers the firstreflector when the ink cartridge is mounted on the cartridge holder, sothat at least one of side walls forming the recess serves as the shadingmember. In such a configuration, because the first reflector is coveredwhen the ink cartridge has been mounted, soils or ink splash on thefirst reflector caused by a printing operation can be reliablyprevented.

The shading member may not shade the optical path when the ink cartridgeis provisionally mounted on the cartridge holder. In such aconfiguration, such an inconvenience that the printing operation isconducted in a provisionally mounted state of the ink cartridge can beavoided.

The ink cartridge detector may further comprise a first engagementmember provided in the ink cartridge, and a second engagement memberprovided in the cartridge holder. The first engagement member may comeinto contact with the second engagement member such that the inkcartridge is retained at a first position in which the shading memberdoes not shade the optical path. In addition, the first engagementmember may engage with the second engagement member such that the inkcartridge is retained at a second position in which the shading membershades the optical path.

In one embodiment, the first engagement member is provided as a convexportion formed on the ink cartridge; the second engagement member isprovided in a free end portion of an elastic member which is supportedby the cartridge holder in a cantilevered manner; the second engagementmember is a V-shaped member including a first slope portion and a secondslope portion so as to convex toward the ink cartridge; the convexportion is brought into contact with the first slope portion when theink cartridge is retained at the first position; and the convex potionis retained by the second slope portion when the ink cartridge isretained at the second position.

Preferably, the optical sensor and the cartridge holder are movablerelative to each other. Here, it is preferable that a plurality of firstreflectors are arranged in a direction of relative movement between theoptical sensor and the cartridge holder. In such a configuration, it ispossible to detect the mounting conditions of a plurality of the inkcartridges by the same optical sensor.

Also, the ink cartridge detector may further comprise a secondreflector, provided in the ink cartridge, which reflects light emittedfrom the light emitter and varies an intensity thereof in accordancewith an ink amount remaining in the ink cartridge. Here, the secondreflector may be operable to form a part of an optical path originatedfrom the light emitter to the light receiver, when the ink cartridge ismounted on the cartridge holder. In such a configuration, it is possibleto detect both the mounting condition of the ink cartridge and theamount of the remaining ink by the same optical sensor.

According to the invention, there is also provided an ink jet printercomprising the above ink cartridge detector.

Further, according to the invention, there is also provided an inkcartridge, operable to be detachably attached to a cartridge holderprovided with a first reflector capable of forming a part of an opticalpath originated from a light emitter of an external optical sensor to alight receiver of the optical sensor, the ink cartridge comprising:

an ink reservoir, storing ink therein;

a second reflector, which reflects light emitted from the light emitterand varies an intensity thereof in accordance with an ink amountremaining in the ink reservoir, the second reflector operable to form apart of an optical path originated from the light emitter to the lightreceiver; and

a shading member, which shades the optical path, which has been formedby the first reflector and the optical sensor, when the ink cartridge ismounted on the cartridge holder.

Preferably, the shading member shades the first reflector from the lightemitted from the light emitter, when the ink cartridge is mounted on thecartridge holder.

Here, a recess may be formed so as to cover the first reflector when theink cartridge is mounted on the cartridge holder, so that at least oneof side walls forming the recess serves as the shading member. Therecess may be shaped as to surround an outer periphery of the firstreflector.

Also, it is preferable that the recess is formed on a face opposing tothe cartridge holder.

The ink cartridge may further comprise a first engagement member. In oneembodiment, the first engagement member comes into contact with a secondengagement member provided in the cartridge holder, such that the inkcartridge is retained at a first position in which the shading memberdoes not shade the optical path. The first engagement member engageswith the second engagement member such that the ink cartridge isretained at a second position in which the shading member shades theoptical path.

Preferably, the second reflector and the shading member are juxtaposedin a direction in which the cartridge holder and the optical sensor areto be moved relative to each other.

BRIEF DESCRIPTION OF THE DRAWINGS

The above objects and advantages of the present invention will becomemore apparent by describing in detail preferred exemplary embodimentsthereof with reference to the accompanying drawings, wherein:

FIG. 1 is a side view schematically showing an interior structure of aprinter;

FIG. 2 is a plan view schematically showing the interior structure ofthe printer;

FIG. 3 is a perspective view of a carriage on which a print head ismounted;

FIG. 4 is a front view of an ink supply section showing a state in whichink cartridges are not mounted.

FIG. 5 is a front view of the ink supply section showing a state inwhich the ink cartridges are mounted;

FIG. 6 is a perspective view of the ink supply section showing the statein which the ink cartridges are not mounted;

FIG. 7 is a perspective view of the ink supply section showing the statein which the ink cartridges are mounted;

FIG. 8 is a perspective view of the ink cartridge as viewed from abottom thereof;

FIGS. 9A to 9C are explanatory views showing detection of mountingcondition and detection of an amount of remaining ink;

FIG. 10 is a sectional view of the ink supply section taken along a lineX-X in FIG. 7, showing a state where the ink cartridge is plenarilymounted; and

FIG. 11 is a sectional view of the ink supply section taken along a lineY-Y in FIG. 7, showing a state where the ink cartridge is provisionallymounted.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

One embodiment of the invention will be described referring to theaccompanying drawings. As shown in FIG. 1, an inlet 11 for insertingpaper P by hand is provided on a front face of a printer 10. An outlet12 for discharging the paper P after printing is provided on an upperface of the printer 10. Inside the printer 10, there is formed a paperfeeding path 13 in a V-shape in a side view extending from the inlet 11to the outlet 12, and a paper feeding roller unit 14 and a print head 15are arranged on the paper feeding path 13. The paper feeding roller unit14 includes a paper feeding roller 16 and a paper holding roller 17which are opposed to each other on both sides of the paper feeding path13, and adapted to clamp and transport the paper P in accordance withdriving rotation of the paper feeding roller 16.

The print head 15 is mounted on a carriage 18 which reciprocates in alateral direction of the paper feeding path 13 (in a direction from theleft to the right in FIG. 2), and adapted to perform dot matrix printingon the paper P. The position of the paper P is regulated by a platen 19.The printing system of the print head 15 is an ink jet system in whichcharacters or images are printed on the paper P by discharging ink, andthe ink used for printing is supplied to the print head 15 from an inksupply section 20 which is provided in a rear area of the printer 10.

The carriage 18 is supported by a pair of front and rear guide shafts21, 22 so as to move from the left to the right, and is forcibly movedin accordance with driving motion of a carriage driving mechanism 23.The carriage driving mechanism 23 includes a cam shaft 24 which isarranged below the front guide shaft 21 in parallel thereto, and acarriage motor 26 for actuating the cam shaft 24 to rotate by way of areduction gear train 25 (FIG. 2). On an outer peripheral face of the camshaft 24, there is formed a cam groove in a spiral shape (not shown),with which a cam follower 27 extending from the carriage 18 is adaptedto be engaged. When the cam shaft 24 is rotated in accordance with thedriving motion of the carriage motor 26, the cam follower 27 is shiftedin an axial direction with spiral shifting action of the cam groove. Inthis manner, it will be possible to reciprocate the carriage 18 from theleft to the right in accordance with normal and reverse drives of thecarriage motor 26.

As shown in FIG. 3, the print head 15 is mounted on an upper part of thecarriage 18. A flat cable 28 and ink tubes 29 having flexibility aredrawn from a side area of the print head 15, and the ink is supplied tothe print head 15 from the ink supply section 20 by way of the ink tubes29. The carriage 18 has a sensor mounting part 18 a which is extendeddownwardly from its rear part, and an optical sensor 30 of a reflectivetype which includes a light emitting element 30 a for emitting a lightbeam to the rear and a light receiving element 30 b for receiving areflective light beam is attached to a back face of the sensor mountingpart 18 a.

As shown in FIG. 4, the ink supply section 20 includes a cartridgeholder 31 which is provided in a rear area inside the printer 10, andtwo ink cartridges 32A, 32B which are detachably mounted on thecartridge holder 31 from the above. As shown in FIG. 8, an ink reservoir34A is partitioned inside the ink cartridge 32A to store secondary ink(for example, colored ink such as cyan, magenta, yellow, red, green,blue). The secondary ink is appropriately discharged from an ink outlet33A formed in a bottom of the ink cartridge 32A. A waste ink reservoir36 is also partitioned inside the ink cartridge 32A to store waste inksupplied from a recovery inlet 35 formed in the bottom. When the inkcartridge 32A has been mounted at a predetermined (specific) position onthe cartridge holder 31, the ink outlet 33A and the recovery inlet 35are communicated with connecting ports 37A, 38 which are formed in abottom of the cartridge holder 31, thus permitting supply of thesecondary ink and recovery of the waste ink.

On the other hand, inside the ink cartridge 32B, there are partitionedan ink reservoir 34B which stores primary ink (for example, black ink)and appropriately discharges the primary ink from an ink outlet 33B in abottom of the ink cartridge 32B. When the ink cartridge 32B has beenmounted at a predetermined (specific) position on the cartridge holder31, the ink outlet 33B is communicated with a connecting port 37B whichis formed in the bottom of the cartridge holder 31, thus permittingsupply of the primary ink.

The ink cartridges 32A, 32B are arranged in a row along a movingdirection of the carriage 18 (the optical sensor 30). The ink cartridges32A, 32B are respectively provided, at positions opposed to a movingpath L (see FIG. 5) of the optical sensor 30 on their front faces, withreflectors (reflectors for detecting an amount of remaining ink) 39A,39B in a shape of prism having transparency. The reflectors 39A, 39Bhave a shape of a right triangle prism, and two prism reflective facesS1, S2 which are at a right angle with respect to each other areprotruded into the ink reservoirs 34A, 34B. As shown in FIG. 9B, whenthe optical sensor 30 is moved to a position opposed to the reflector39A and a light is emitted thereto, the emitted light is reflected atthe prism reflective faces S1, S2 sequentially while passing interiorsof the reflector 39A, and received by the light receiving element 30 b.When the optical sensor 30 is moved to a position opposed to thereflector 39B and a light is emitted thereto, the emitted light isreflected at the prism reflective faces S1, S2 sequentially whilepassing interiors of the reflector 39B, and received by the lightreceiving element 30 b.

Reflectivity (refraction index) of the prism reflective faces S1, S2 islow in the case where levels of the remaining ink in the ink reservoirs34A, 34B are higher than the prism reflective faces S1, S2, and is highin the case where the levels of the remaining ink are lower than theprism reflective faces S1, S2. In short, in a state where the prismreflective faces S1, S2 are in contact with the ink as shown in FIG. 9A,an emitted light beam of the optical sensor 30 is absorbed by the ink tohave a low reflectivity (the intensity of reflected light is made low),and in a state where the prism reflective faces S1, S2 are in contactwith air as shown in FIG. 9B, the light beam is not absorbed by the inkto have a high reflectivity (the intensity of reflected light is madehigh). In this manner, it will be possible to detect the amount of theremaining ink (presence or absence of the ink at the predeterminedlevel) in the ink cartridges 32A, 32B on the basis of a value detectedby the light receiving element 30 b of the optical sensor 30.

As shown in FIGS. 4 and 6, on the bottom of the cartridge holder 31, tworeflectors (reflectors for detecting mounting condition) 40A, 40B arefixed in a row along the moving direction of the carriage 18 (the movingpath L of the optical sensor 30), in an upwardly protruding posture.Each of the reflectors 40A, 40B has a prism part 40 a in a shape of aright triangle prism, and reflective light paths of the optical sensor30 are formed by two prism reflective faces S3, S4 which are at a rightangle with respect to each other, in the same manner as the reflectors39A, 39B for detecting the amount of the remaining ink. On the otherhand, recesses (hollowed parts) 41A, 41B are integrally formed inrespective lower portions of the ink cartridges 32A, 32B. When the inkcartridges 32A, 32B have been mounted at the predetermined positions ofthe cartridge holder 31, the reflectors 40A, 40B are inserted into therecesses 41A, 41B, and the surroundings are covered. On this occasion,shield parts 42A, 42B which are integrally formed on one side faces ofthe recesses 41A, 41B (wall portions opposed to the optical sensor) areinterposed between the optical sensor 30 and the reflectors 40A, 40B, soas to shield light paths (irradiation paths and reflective paths)between the optical sensor 30 and the reflectors 40A, 40B.

As shown in FIGS. 4 and 9C, in the state where the ink cartridges 32A,32B are not mounted on the cartridge holder 31, the reflectors 40A, 40Bare exposed. When the optical sensor 30 is moved to a position opposedto the reflector 40A in this state, the emitted light is sequentiallyreflected at the reflective faces S3, S4 while passing the interior ofthe reflector 40A, and will enter the light receiving element 30 b. Whenthe optical sensor 30 is moved to a position opposed to the reflector40B in this state, the emitted light is sequentially reflected at thereflective faces S3, S4 while passing the interior of the reflector 40B,and will enter the light receiving element 30 b. On the other hand, asshown in FIGS. 9A and 9B, in the state where the ink cartridges 32A, 32Bhave been mounted on the cartridge holder 31, front areas of thereflectors 40A, 40B are covered with the shield parts 42A, 42B. When theoptical sensor 30 is moved to the position opposed to the reflector 40Ain this state, the emitted light is shielded by the shield part 42A, andwill not reach the reflector 40A nor the light receiving element 30 b ofthe optical sensor 30. When the optical sensor 30 is moved to theposition opposed to the reflector 40B in this state, the emitted lightis shielded by the shield part 42B, and will not reach the reflector 40Bnor the light receiving element 30 b of the optical sensor 30.

In this manner, it is possible to detect the mounting condition of theink cartridges 32A, 32B by the optical sensor 30, without providing theink cartridges 32A, 32B with the reflectors for detecting the mountingcondition. Moreover, in the state where the ink cartridges 32A, 32B arenot mounted on the cartridge holder 31 as described above, since thelight receiving element 30 b is always subjected to the light emission,an exterior turbulent light will not influence detection results of themounting condition of the ink cartridges 32A, 32B, even though theexterior turbulent light is emitted to the light receiving element 30 b.Further, in the state where the ink cartridges 32A, 32B have beenmounted on the cartridge holder 31, since the reflectors 40A, 40B arecovered with the recesses 41A, 41B, the ink will not adhere to thereflectors 40A, 40B, even though the ink is splashed during the printingoperation. As a result, it is possible to prevent an erroneous detectioncaused by ink adhering to the reflectors 40A, 40B.

FIG. 10 is a sectional view of the ink supply section taken along a lineX-X in FIG. 7, showing a state where the ink cartridge is plenarilymounted, and FIG. 11 is a sectional view of the ink supply section takenalong a line Y-Y in FIG. 7, showing a state where the ink cartridge hasbeen provisionally mounted. As shown in these drawings, there areprovided, in a rear part of the cartridge holder 31, two lock plates43A, 43B in an upright manner. The lock plates 43A, 43B are elasticplate members formed with V-shaped locking portions 44A, 44B in theirupper end portions. When the ink cartridges 32A, 32B have been mountedon the cartridge holder 31 from above, convex portions 45A, 45Bprojected from back faces of the ink cartridges 32A, 32B lie on the lockportions 44A, 44B of the lock plates 43A, 43B, as shown in FIG. 11, tohold the ink cartridges 32A, 32B in a provisionally mounted state. Onthis occasion, the shield parts 42A, 42B of the ink cartridges 32A, 32Bare located above the prism parts 40 a of the reflectors 40A, 40B, andthe light paths between the optical sensor 30 and the reflectors 40A,40B will not be shielded.

Further, in the above described provisionally mounted state, when theink cartridges 32A, 32B are pushed downward, the lock plates 43A, 43Bare pressed by the convex portions 45A, 45B to be tilted so as to onceretreat backward, and then, ride over the convex portions 45A, 45 b tobe tilted so as to be returned forward. After the lock plates 43A, 43Bhave been tilted to be returned, the locking portions 44A, 44B areengaged with upper parts of the convex portions 45A, 45B as shown inFIG. 10, and the ink cartridges 32A, 32B are held (locked) in theirmounting positions. On this occasion, the shield parts 42A, 42B of theink cartridges 32A, 32B are interposed between the prism parts 40 a ofthe reflectors 40A, 40B and the optical sensor 30 to shield the lightpath of the optical sensor 30.

As described above, according to this embodiment, the printer 10 isconstructed by including the optical sensor 30 of a reflective typewhich projects the light to the cartridge holder 31 to detect themounting conditions of the ink cartridges 32A, 32B on the basis of thereflective light, the reflectors 40A, 40B which are provided on thecartridge holder 31 to form the reflective light path of the opticalsensor 30, and the shield parts 42A, 42B which are provided in the inkcartridges 32A, 32B, and adapted to shield the light path of the opticalsensor 30 when the ink cartridges 32A, 32B have been mounted on thecartridge holder 31. In short, although the mounting condition of theink cartridges 32A, 32B is detected by the optical sensor 30 of thereflective type, necessity for providing the ink cartridges 32A, 32Bwith the reflectors for detecting the mounting condition can beeliminated. Therefore, not only reduction of the cost for the inkcartridges 32A, 32B can be attained, but also, an erroneous recognitionof the mounting condition due to soils such as ink splash on thereflectors or an exterior turbulent light can be prevented.

Moreover, because the reflectors 40A, 40B are fixed members which areintegrally provided in the bottom of the cartridge holder 31, ascompared with the reflectors 40A, 40B formed of movable members, notonly the structure can be simplified, but also reliability of detectingthe mounting condition can be enhanced.

Further, because the shield parts 42A, 42B are integrally formed in thelower parts of the ink cartridges 32A, 32B, the number of the componentsand the production steps of the ink cartridges 32A, 32B can bedecreased.

Still further, because the ink cartridges 32A, 32B have the recesses41A, 41B which cover the reflectors 40A, 40B when they have been mountedon the cartridge holder 31, and the shield parts 42A, 42B are formed atthe one side faces of the recesses 41A, 41B, the reflectors 40A, 40B canbe protected when the ink cartridges have been mounted, and defectivedetection due to soils such as ink splash or damage of the reflectors40A, 40B can be prevented.

Furthermore, the shield parts 42A, 42B will not shield the light path ofthe optical sensor 30 when the ink cartridges 32A, 32B are provisionallymounted on the cartridge holder 31, and therefore, problems such asconducting the printing operation in the provisionally mounted state ofthe ink cartridges 32A, 32B can be avoided.

Still further, because the cartridge holder 31 and the optical sensor 30are relatively movable with respect to each other, it is possible todetect the mounting conditions of a plurality of the ink cartridges 32A,32B, and to detect the amount of the remaining ink in the ink cartridges32A, 32B by the same optical sensor 30.

Still further, the cartridge holder 31 is provided with a plurality ofthe reflectors 40A, 40B which are arranged in a row along the directionof the relative movement of the optical sensor 30 (along the line Lshown in FIGS. 4 and 5), and accordingly, the same optical sensor 30 candetect the mounting conditions of the plurality of the ink cartridges32A, 32B.

In addition, the ink cartridges 32A, 32B are provided with thereflectors 39A, 39B for detecting the amount of the remaining ink,enabling the amount of the remaining ink to be detected by the opticalsensor 30, and accordingly, the same optical sensor 30 can detect theamounts of the remaining ink as well as the mounting conditions of theink cartridges 32A, 32B.

Although one of the embodiments according to the invention has beendescribed heretofore, the present invention is not limited to thosematters shown in the above described embodiment, but may include such ascope as those skilled in the art can make modification and applicationof the invention, on the basis of the description in the claims and inthe detailed description of the invention, and the well known art.

For example, although in the above described embodiment, the shield partis formed on one side face of the recess which is integrally formed inthe ink cartridge, the shield part may be in any shape, provided that itcan shield the light path of the optical sensor 30 when the inkcartridge has been mounted on the cartridge holder. For example, theshield part may be formed in a hook-like shape (L-shape) on the one sideface of the ink cartridge.

Moreover, although in the above described embodiment, the ink cartridgesare mounted on the printer body, the invention can be realized in theprinter in which the ink cartridges are mounted on the carriage.Specifically, by providing the reflectors on the cartridge holder whichis mounted on the carriage, and detecting them by the optical sensorwhich is provided on the printer body, similar function and advantageouseffects to those in the above described embodiment can be obtained.

According to the present invention as has been herein before described,although the mounting condition of the ink cartridge is detected by theoptical sensor of a reflective type, necessity for providing the inkcartridge with the reflectors for detecting the mounting condition iseliminated, and not only reduction of the cost for the ink cartridge canbe attained, but also, an erroneous recognition of the mountingcondition due to soils such as ink splash on the reflectors or anexterior turbulent light can be prevented.

1. An ink cartridge, comprising: an ink reservoir for storing ink; a reflector arranged so that light emitted from an external light emitter is (i) absorbed by the ink when the reflector is in contact with the ink and (ii) reflected to an external light receiver when the reflector is not in contact with the ink; and a shading member for blocking a light path originating at the external light emitter and terminating at the external light receiver when the ink cartridge is mounted on an external cartridge holder, wherein the reflector and the shading member are juxtaposed in a direction in which the external light emitter moves.
 2. The ink cartridge of claim 1, wherein the reflector and the shading member are located on one side face of the ink cartridge.
 3. The ink cartridge of claim 1, wherein the shading member and a bottom of the ink cartridge cooperate to define a hook-like shape. 